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1. Building Pathology > 06 General Defects > Flashcards

06 General Defects Flashcards

1
Q

Name 10 defects you would commonly find in a Georgian building.

A
  1. Leaning chimneys
  2. Overloading of roof due to change of materials (e.g. concrete tiles)
  3. Removal of chimney breasts but not the stack
  4. Blocked internal gutters
  5. Brick walls prone to distortion due to lack of restraint at each floor level
  6. Damp penetration through solid walls
  7. Rotting timber joists that are built into external wall
  8. Dry rot caused by poor cross-ventilation in narrow, long terraces
  9. Shallow foundations causing dropping of central spine wall
  10. Damp basements
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2
Q

Name 10 defects you would commonly find in a Victorian building.

A
  1. Leaning chimneys
  2. Overloading of roof due to change of materials (e.g. concrete tiles)
  3. Removal of chimney breasts but not the stack
  4. Damp penetration through solid walls
  5. Rotting timber joists that are built into external wall
  6. Wall tie failure (if a cavity wall, particularly in black ash mortar)
  7. Differential settlement of bay windows (little to no foundations)
  8. Rising damp caused by lack, failure or bridging of DPC
  9. Blocked air vents to ground floors, causing dry rot
  10. Lead water pipes
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3
Q

What defects would you expect to see in properties built between 1945-1970?

A

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4
Q

Name 10 defects you would commonly find in a 1960s high-rise office block.

A
  1. Flat roof problems
  2. Parapet walls (loose copings)
  3. Poor workmanship (inadequate re-bar cover)
  4. Concrete defects - carbonation/chloride attack
  5. Deleterious material - asbestos/HAC/brick slips
  6. Cold bridges
  7. Overloading of floors (filing cabinets)
  8. Poor access and egress - narrow staircases, change in levels
  9. Brittle metal windows
  10. Corrosion of steel fixings
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5
Q

A 1960s building has misaligned concrete panels - what are the possible causes and what investigates would you undertake?

A

???

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6
Q

Name some common defects in a 1970s building.

A

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7
Q

In a steel frame brick wall 1950s building, what particular defects would you be looking for?

A

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8
Q

What defects would you commonly find in a CLASP building?

A
  1. Penetrating damp through failed joints
  2. Poor gaskets around windows
  3. Pitched fibre drainage deformed, collapsed or become blocked
  4. Cold bridges
  5. Excessive solar gain to some elevations
  6. Poor U-values of the building fabric
  7. Asbestos - boarding around steel members/ceiling tiles/pipe lagging/floor coverings etc
  8. Rotting of timber floors and roofs in earlier Marks
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9
Q

What is cold bridging?

A
  • Cold bridging occurs in localised spots where the nature of the construction allows heat to escape through the structure at a higher rate than normal
  • This creates situations where there may be quite low internal surface temperatures which can encourage patches of local condensation
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10
Q

Where would you expect to find cold bridging?

A
  1. Concrete lintels crossing cavity walls
  2. Uninsulated box-section lintels
  3. Jambs and sills with returned blockwork inner leaf
  4. Floor slabs lacking insulated upstands
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11
Q

What is radon and why is it a problem?

A
  1. Natural radioactive gas that cannot be seen, smelt, heard or felt
  2. Emanates from minute amounts of uranium that occur naturally in all rocks and soils
  3. Most radon disperses harmlessly into the air outside but some will collect in spaces under or within buildings
  4. Exposure to high levels of radon can increase the risk of developing lung cancer
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12
Q

In which areas of the UK are you most likely to come across radon?

A

Some parts of the country (e.g. the West Country, Derbyshire and Northamptonshire) have higher levels than elsewhere

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13
Q

Other than radon, what other ground gases are problematic and why?

A
  1. Methane - explosive in air at concentrations between 5-15%, generated by the anaerobic (absence of oxygen) degradation of organic material
  2. Carbon dioxide - dlassed as highly toxic - can result in headaches and shortness of breath
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14
Q

Name some legislation that detail requirements when considering ground gases.

A
  1. Town and Country Planning Act 1990 - potential for contamination and risk from landfill and ground gases must be considered during development
  2. Environmental Protection Act 1990 - where potential for significant harm exists to a development (either existing or proposed), the local authority can enforce appropriate remediation or mitigation
  3. Building Regulations Approved Document C - where there is a potential risk, further investigation is required to determine whether gas measures are required and what level of protection is necessary
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15
Q

How would you find out whether radon gas was a problem in a particular area?

A
  1. Desk-based study of the history and geology of the area and any additional information such as mining or landfill activities
  2. Public Health England (formerly the Health Protection Agency) and the British Geological Survey publishes maps of radon affected areas across and sets threshold levels for both commercial and residential properties
  3. Maps can also be found in BRE Report BR 211 (Radon)
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16
Q

What steps would you need to take if your client wanted to build in an area where radon gas was present?

A

Passive (basic protection):

  • Usually achieved by increasing the airtightness of the DPM and extending it across the external leaf of brickwork
  • Can also improve ventilation under suspended timber and concrete floors by installing airbricks

Active:

  • Used where risks are higher
  • Sump pumps connected to a fan in order to extract
  • May be required if protective membrane is damaged

Alarm Systems:

  • Designed to trigger when gas concentration reach a certain level
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17
Q

What is Japanese Knotweed and when was it introduced?

A
  • A hardy bamboo-like plant that grows quickly and strongly
  • Introduced to the UK in the mid-19th Century
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18
Q

What legislative controls exist for Japanese Knotweed?

A
  1. Banned in the Wildlife and Countryside Act 1981, making it an offence to plant or cause the growth of Japanese Knotweed
  2. The Environmental Protection Act 1990 also contains a number of legal provisions, designating contaminated soil as controlled waste, meaning only properly licensed organisations can remove it
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19
Q

What problems are associated with Japanese Knotweed?

A
  • Japanese Knotweed is extremely invasive and can cause serious damage to:
    • Drains and buried services - can exploit cracks and gaps in pipework
    • Patios, paths and drives - can grow between joints
    • Boundary and retaining walls - can undermine walls with shallow foundations
    • Outbuildings - can overwhelm lightweight structures (sheds, garages etc.)
  • There are claims that damage to building foundations can also occur, however this is rare
  • The plant can remain dormant, so eradication may be difficult to guarantee
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20
Q

How would you identify Japanese Knotweed?

A

RICS Information Paper ‘Japanese Knotweed’ - Appendix C contains an identification chart throughout the seasons, namely:

  1. Hollow stems within distinct raised nodes (like bamboo) which develop purple speckles
  2. Can reach heights up to 3-4m in its growing season (summer) and grow in dense clumps (aka ‘stands’)
  3. Leaves are lush green and flat heart/shield shaped, approx. 70-140mm long and 50-120mm wide
  4. Flowers are small, creamy white spikes of length approx. 60-150mm
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21
Q

How would you remediate the problems caused by Japanese Knotweed?

A

Specialist contractor required, who may specify:

  1. Excavation/removal of plant and roots - can extend 3m down and 7m across
  2. Biological control - use of ‘pests’ that attack and control the plant
  3. Chemical control - use of specialist herbicides (can take up to 3 years to completely eradicate)
  4. On-site burial - may require a specialist root barrier membrane
22
Q

What is Giant Hogweed and when was it introduced?

A

Introduced as an ornamental plant in the 1890s

23
Q

What legislative controls exist for Giant Hogweed?

A

Banned in the Wildlife and Countryside Act 1981, making it an offence to plant or cause the growth of Giant Hogweed

24
Q

What are the problems with Giant Hogweed?

A
  1. Contact with its sap (present inside the stem and on the hairs that cover the leaves and stem) makes skin highly sensitive to ultra-violet light
  2. No discomfort is experienced until around 15-20 hours after exposure, where burns develop that quickly turn into large watery blisters, which recede and leave scars that remain highly photosensitive for years or even life
  3. Can cause blindness if contact is made with the eyes
  4. Suggestion that toxins within the sap are carcinogenic and could cause cancer or result in malformations of unborn foetuses in pregnant women
25
Q

How would you identify Giant Hogweed?

A
  1. Often grows between 3-5m over four years
  2. Stems - hollow, purple (or green speckled with purple) and covered in fine hairs
  3. Leaves - dark green, coarsely toothed, hairy like stems, measuring up to 2m across
  4. Flowers - numerous small and white flowers, emerge in mid to late summer on top of the stems in umbrella-like clusters
26
Q

How would you remediate the problems caused by Giant Hogweed?

A

Specialist contractor required, who may specify:

  1. Herbicidal treatment - effective, but must be undertaken regularly over several years (seeds can remain dormant for up to 7 years)
  2. Dig up and dispose as controlled waste (may need to excavate up to 4m around plants due to seed spread)
  3. Combination of both
27
Q

What should you do if you come into contact with Giant Hogweed?

A
  1. Wash immediately with soapy water any area of skin that comes into contact
  2. If contact is made with the eyes, flush immediately with water
  3. Cover affected areas and keep out of sunlight for at least 48 hours
  4. Seek medical advice
28
Q

What is Regent Street Disease and how is it caused?

A
  1. Also known as steel frame corrosion
  2. Affects buildings constructed circa 1905 onwards (i.e. when steel became a popular construction material)
  3. Load-bearing frames of steel were clad with stone, brickwork or terracotta (notched around the steel frame) with the voids between the two filled with low grade mortar
  4. Mortar compaction was poor and often contained lumps of brick or stone, which increased the number of voids
  5. Inevitable shrinkage cracks meant that water and oxygen could penetrate the fabric, facilitating corrosion of the steel
29
Q

What problems are associated with Regent Street Disease?

A
  1. Corroded steel expands at least four times its original volume
  2. Due to the infilled voids around the steel, expansion inevitably results in cracking of façade, allowing more water to penetrate
  3. In extreme cases, loss of support can result from horizontal cracking, causing collapse of pieces of stone or brick
30
Q

How would you identify Regent Street Disease?

A
  1. Vertical or horizontal cracking reflecting the location of the steel frame
  2. Physically opening up the façade is an option, although disruptive and may require consent if listed
  3. NDT (non-destructive testing) systems are also available to determine the extent of the corrosion or prognosis for future deterioration
31
Q

What steps would you recommend to remediate Regent Street Disease?

A
  1. Expose, clean and protect the steel - expensive and disruptive
  2. Provide a corrosion barrier to the steel and then create a void around it so if further corrosion does occur, it will not result in cracking
  3. Cathodic Protection Systems
32
Q

Give an example of an interesting pathology issue you have had to deal with?

A

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33
Q

What are the common causes of spalled brickwork?

A

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34
Q

What is frost action?

A
  1. Caused by a combination of excessive wet brickwork and freezing temperatures
  2. When water turns to ice, it expands
  3. The repeated freeze-thaw cycle produces stresses on the brick causing it to spall (the face flaking/crumbling off)
35
Q

Why may the use of strong mortars exacerbate the problem of frost action?

A

Strong mortar tends to suffer from shrinkage cracks which will allow water to penetrate, and because strong mortars are not as ‘breathable’, it will be difficult for the water to evaporate

36
Q

A white powdery substance has appeared on the surface of some new brickwork. What might it be and what can you do about it?

A

Efflorescence:

  • May only be problematic in cases of rising damp, as the crystals can sometimes block pores in brickwork, thus preventing evaporation and driving damp higher up the wall
  • Can be brushed off if appearance is causing a concern
37
Q

You notice the gable wall of an end terrace property is bowing - what could be the reason for this?

A

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38
Q

What is ‘bookend effect’ and how is it caused?

A
  1. Bulging of a flank wall due to lack of lateral restraint, often due to floor joists running parallel with the wall and/or lack of buttresses
  2. Common in buildings built before the mid-1980s however can occur later if alteration are undertaken (e.g. removing a chimney breast that was previously acting as a buttress, removing an internal perpendicular wall or even creating an opening in such a wall)
  3. Problem often accentuated by the presence of the staircase adjacent to the flank wall
39
Q

How can ‘bookend effect’ be remediated?

A

Remedial works involves mechanical insertion of metal tie rods along the length of wall

40
Q

What problems are likely to be associated by rendering over external brickwork?

A

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41
Q

What issues may there be with a partial fill cavity wall in respect of workmanship?

A

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42
Q

What is snapped header defect and how is it caused?

A
  1. Often used to save money (facing bricks were much more expensive than commons and therefore ‘snapping’ the brick in two could provide two facing brick heads)
  2. Header bricks were traditionally used to tie solid walls together
  3. Snapped headers cause defects as there is a lack of tying-in between the inner and outer face
43
Q

How can you tell when timber structural members are deflected or bowed?

A

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44
Q

A hall floor is re-laid but the screed fails - what are the possible reasons for this?

A

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45
Q

How can stonework be repaired?

A

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46
Q

What causes rainwater goods to become defective?

A

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47
Q

How would you determine if a drainage run was free from and breaks or blockages?

A

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48
Q

What action might be necessary to free up sliding sash windows that are sticking?

A

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49
Q

What defects would you associate with portal framed warehouse units?

A

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50
Q

What is cut edge corrosion?

A

Occurs when the protective coating on metal sheeting peels back at lap joints (usually where it has been cut), exposing the base metal to risk of corrosion, which can cause section loss

51
Q

How do you repair cut edge corrosion?

A
  1. Remedial work involves cleaning the effective area, removing the defective coating (e.g. by chemical stripping) and treating the sheet lap with a silicone based paint
  2. Current guidance states cut edges should be painted before installation, however this is often neglected
52
Q

What problems can arise from using two different metals next to each other?

A

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1. Building Pathology (7 decks)

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